Graeme Samuel told a parliamentary inquiry into animal extinction on Thursday the current lack of data hampered efforts to protect the environment.

His comments come on the back of his critical interim report into the Environment Protection and Biodiversity Conservation Act.

The review released last week found federal environmental protection laws were ineffective and more responsibility should be handed to the states.

"You've got an act that focuses so much on process and so little on outcomes," Mr Samuel said on Thursday.

"The act is very complex. We've got duplications of processes between the Commonwealth and states and territories. There are inconsistencies."

He said legal terms like acceptable or unacceptable were "fuzzy" and unclear.

Precise language like saying a development must cause "no net loss of koalas" would be specific enough to enforce.

Boosted data would help authorities quantify what "no net loss" would look like, Mr Samuel said.

Conservation groups also fronted the inquiry, pointing to a lack of community trust in the EPBC Act.

Environmental Defenders Office policy director Rachel Walmsley was concerned at handing power back to the states.

"The key issue of concern is the weak state (environmental) laws," Ms Walmsley said.

"There's also the international responsibilities the federal government has on the environment."

Australian Associated Press